A present invention generally relates to a semiconductor laser source unit, and particularly to a semiconductor laser source unit suitable for an optical system having a light source such as a facsimile machine, a laser printer, and a copier.
Currently, a semiconductor laser is widely used as a light source for an optical system. As is well known, a laser beam emitted from a semiconductor laser unit is a divergent light. For this reason, generally, a packaged semiconductor laser unit including a semiconductor laser diode or chip is combined with a collimating lens so as to construct a semiconductor laser source unit, which emits a collimated laser beam.
A conventional semiconductor laser source unit is disclosed in U.S. Pat. No. 4,763,334. The disclosed semiconductor laser source unit includes a semiconductor laser unit supported by a metal support plate, and a collimating lens which consists of a plurality of lenses and is supported by the metal support plate so as to be placed in position for receiving a laser beam emitted from the semiconductor laser unit and collimating it. The above-mentioned structural parts are covered by an electrically insulating cover so as to construct a unit of a semiconductor laser source. As is well known, it is required to position the semiconductor laser unit and the collimating lens with extremely high precision. For this reason, the collimating lens is movably fastened to the metal support plate so that the position of the collimating lens can be adjusted in X and Y directions.
However, the adjustment of position of the collimating lens is very troublesome. Additionally, the size of the semiconductor laser source unit is large, because the metal support plate must be used to support the semiconductor laser unit and the collimating lens consisting of a plurality of lenses.
A single aspherical lens is disclosed in Japanese Laid-Open Patent Application Nos. 57-201210 and 58-17409. The disclosed aspherical lens is used as an objective lens in an optical pick-up. The aspherical lens and a recording disc having recording track formed on a surface thereof, for example, are provided so as to be relatively movable.
One may conceive that the disclosed single aspherical lens is substituted for the collimating lens of the semiconductor laser source unit disclosed in U.S. Pat. No. 4,763,334. The use of a single aspherical lens would contribute to reducing the working of adjusting the lens position. However, even by the above-mentioned conceivable combination, it is impossible to extremely reduce the size of the semiconductor laser source unit.